Research Paper

Investigation of the first recent crayfish plague outbreak in Ireland and its subsequent spread in the Bruskey River and surrounding areas

¹ Marine and Freshwater Research Centre, Department of Natural Resources & the Environment, School of Science and Computing, Galway-Mayo Institute of Technology, Dublin Road, Galway H91 T8NW, Ireland
² Department of Biology, University of Padova, via Ugo Bassi 58/B, 35131 Padova, Italy
³ Marine Institute, Rinville, Co. Galway H91 R673, Ireland
⁴ Irish Farmers Association, Irish Farm Centre, Bluebell, D12 YXW5 Dublin 12, Ireland
⁵ Department of Zoology, Trinity College Dublin, Dublin 2, Ireland
⁶ Department of Housing, Local Government and Heritage, National Parks and Wildlife Service, 90 King Street North, Dublin D07 N7CV, Ireland

^* Corresponding author: luca.mirimin@gmit.ie

Received: 14 September 2021
Accepted: 22 March 2022

Abstract

White-clawed crayfish (Austropotamobius pallipes) is a keystone species found in western European freshwater bodies, where it has suffered drastic declines due to pathogens, competition with non-indigenous crayfish species (NICS) and habitat deterioration. In Ireland, populations of (naturalised) A. pallipes have been considered healthy and abundant mainly because no diseases or NICS have been reported in the past decades. The present study investigated a sudden mass mortality event that occurred in the Erne catchment in 2015. Molecular analysis confirmed that the cause of the event was infection by the oomycete Aphanomyces astaci (the causative agent of the crayfish plague). While in 2015 the spread of the pathogen appeared to remain confined to the outbreak’s epicentre and nearby upstream waters, follow up surveys using conventional methods and environmental DNA (eDNA) approaches indicated that by a year later (2016), the pathogen was still present and had spread downstream beyond Lough Gowna. No NICS were detected during the surveys conducted. This crayfish plague outbreak is of grave concern to Irish white-clawed crayfish and associated ecosystems.